Intermolecular Enantioselective Amination Reactions Mediated by Visible Light and a Chiral Iron Porphyrin Complex.

In the presence of 1 mol % of a chiral iron porphyrin catalyst, various 3-arylmethyl-substituted 2-quinolones and 2-pyridones underwent an enantioselective amination reaction (20 examples; 93-99 % ee). The substrates were used as the limiting reagents, and fluorinated aryl azides (1.5 equivalents) served as nitrene precursors. The reaction is triggered by visible light which allows a facile dediazotation at ambient temperature. The selectivity of the reaction is governed by a two-point hydrogen bond interaction between the ligand of the iron catalyst and the substrate. Hydrogen bonding directs the amination to a specific hydrogen atom within the substrate that is displaced by the nitrogen substituent either in a concerted fashion or by a rebound mechanism.

Catalytic Enantioselective de novo Construction of Chiral Arenes through Desymmetrizing Oxidative [4+2]-Cycloaddition.

Central chirality in arene derivatives arising out of unsymmetrically substituted arene ring is a fascinating yet rarely explored research topic. Here, we report a desymmetrization approach to centrally chiral unfunctionalized arenes, which is enabled by the enantioselective de novo construction of the arene ring. This operationally simple protocol is based on a [4+2]-cycloaddition between polycyclic meso-cyclohexenediones and α,ß-unsaturated aldehydes, and doesn't usually require any external oxidant. Catalyzed by a diphenylprolinol silyl ether, this reaction proceeds via dienamine intermediate and greatly simplifies the access to diversely substituted chiral arenes with outstanding enantioselectivities.

Catalytic Enantioselective Desymmetrizing Fischer Indolization through Dynamic Kinetic Resolution.

The first catalytic enantioselective Fischer indolization of prochiral diketones containing enantiotopic carbonyl groups is developed and shown to proceed through dynamic kinetic resolution (DKR). Catalyzed by the combination of a spirocyclic chiral phosphoric acid and ZnCl2 (Lewis acid assisted Brønsted acid), this direct approach combines 2,2-disubstituted cyclopentane-1,3-diones with N-protected phenylhydrazines to furnish cyclopenta[b]indole derivatives containing an all-carbon quaternary stereocenter with good to excellent enantioselectivities.

Enantioselective [4 + 2]-Annulation of Azlactones with Copper-Allenylidenes under Cooperative Catalysis: Synthesis of α-Quaternary α-Acylaminoamides.

The first enantioselective decarboxylative [4 + 2]-annulation of ethynyl benzoxazinanones with azlactones has been developed under cooperative copper and bifunctional tertiary aminourea catalysis. This direct and modular approach combines dipolar copper-allenylidene intermediates with azlactone enolates and allows for the synthesis of α-quaternary α-acylaminoamides as a single diastereomer generally in high yields with good to excellent enantioselectivities (up to 99:1 er).